1. Field of the Invention
The present invention relates to a method of enhancing the passive thermal management of electronic packages. Moreover, the invention is directed to the provision of an electronic package consisting of a vertically-oriented substrate, such as a printed circuit board or the like, a heat-generating electronic module, for example, containing at least one chip which is positioned on a substrate, and a cover plate located adjacent to the module at a predetermined spaced relationship therefrom. The cover plate includes at least one opening located adjacent the module at a predetermined location relative thereto so as to ensure a maximum cooling air flow impinging on the module, and which air flow thereafter passes upwardly between the substrate and the cover plate. Pursuant to a further aspect of the invention, the latter is directed to the provision of a heat-sink structure for the module, which is adapted to project through the opening formed in the cover plate or to lie flush therewith.
In passive thermal management, or essentially natural convective cooling of electronic packages, reliance is normally placed on a buoyancy-induced air flow around a heated module in order to thermally manage or regulate the temperature of the module during operation of the electronic package. The air flow is propagated on the basis of the phenomenon that warm air possesses a lower density than the surrounding cold air, and therefore will attempt to flow upwardly. This results in the cold air from the surroundings being drawn in and upwardly as a replacement for the warm air, thereby generating a buoyancy-induced, or natural convection air flow. This type of passive thermal management is extremely desirable wherever it can be applied inasmuch as it does not require the utilization of any external energy source to induce the air flow. Furthermore, such a physical set-up, or construction is extremely reliable inasmuch as there is no necessity for the provision of fans or blowers, and the therewith associated costs and potential equipment failures. However, a problem which is encountered is that natural convection air flows are typically weak; in effect, the flow velocity and flow rate are low and also is not well-controlled so that the exact nature of the flow regime or course is by default, rather than by design.
In order to obviate the drawbacks and limitations encountered in the aspect of providing adequate cooling of electronic packages during operation thereof through passive thermal management or natural convection, the air flow is controlled in order to optimize heat transfer from the locations which are of interest, essentially from the module. This is of particular significance in portable systems, such as laptops, where energy, space and weight are severely restricted, thus rendering the use of forced convection undesirable from the standpoint of space, weight and expensive equipment having to be installed in such laptops or similar portable or personal computers.
2. Field of the Prior Art
Although various publications are currently in existence in the technology which are directed to different aspects in providing cooling to electronic packages in order to impart thermal management thereof, these are primarily directed to the so-called forced convection or air flow arrangements, which are cumbersome and space-consuming, energy operated and expensive to install and maintain, while being subject to equipment failure.
U.S. Pat. No. 5,021,924, to Kieda et al., discloses a semiconductor cooling device including a forced convection impingement arrangement for a multi-chip module. There is no disclosure of a natural convection or passive thermal management method for electronic packages.
U.S. Pat. No. 5,467,815, to Haumann et al., discloses an apparatus for impingement cooling including a trapezoidal heat-sink array for the forced convection impingement cooling of a surface. This is a fundamentally differing arrangement with respect to the present natural convection, or passive thermal management, of electronic packages.
U.S. Pat. No. 5,592,363, to Atarashi et al., pertains to an electronic apparatus which incorporates a forced convection thermal management system similar to that of U.S. Pat. No. 5,021,924 and does not direct itself to the natural convection cooling, or passive thermal management, of electronic packages.
U.S. Pat. No. 5,604,665, to Chrysler et al., pertains to a forced convection impingement cooling system for multi-components which includes the ability to tune thermal performance through the use of flow restrictions. This is distinct from the natural convection, or passive thermal management method for electronic packages, as in the present invention.
U.S. Pat. No. 5,022,462, to Flint et al., discloses a flexible finned heat exchanger which utilizes a forced convection air flow for multi-chip applications, and does not define the passive thermal management, or natural convection cooling, of electronic packages.